Heating device



FIG. 1 is a perspective view of the design;

FIG. 2 is a plan view of the top of the design;

FIG. 3 is a plan view of the bottom of the design;

FIG. 4 is an elevational view of one side of the design;

FIG. 5 is an elevational view of the other side of the design;

FIG. 6 is an elevational view of the front of the design; and,

FIG. 7 is an elevational view of the rear of the design. 

The ornamental design for a “heating device,” as shown and described. 